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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Another thing- the rules say nothing about multiple stages. A single bottle pressure vessel would still allow the possibility of a boosted dart. Do we want to allow this? I'd be fine if we did, but it might be getting away from the intention of the competition. Are we trying to see who can launch a pop bottle the highest, or just using them as a pressure vessel so everyone can compete?

SaskAlex wrote:Another thing- the rules say nothing about multiple stages. A single bottle pressure vessel would still allow the possibility of a boosted dart. Do we want to allow this? I'd be fine if we did, but it might be getting away from the intention of the competition. Are we trying to see who can launch a pop bottle the highest, or just using them as a pressure vessel so everyone can compete?

We could put something in there forbidding multiple stages with a link to the multistage competition we already have in place. Does it have to be that clear? I figured that a competitor interested in a multistage rocket would not be looking at this competition. The easiest way would be to insist that the rocket return in one piece (we already require a single bottle as the pressure vessel).

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

Well while we're at name change suggestions I feel compelled to mention that these are BYOB events...

On a more serious note, I like these rules. I think a "youth" division should be added so that kids can compete at their own level but I recognize that can be very hard to set limits (and enforce) on how much adults can help.

I do disagree about allowing heat modifications as suggested above because that dilutes the meaning of "unmodified".

WRA2 wrote:We could put something in there forbidding multiple stages with a link to the multistage competition we already have in place. Does it have to be that clear? I figured that a competitor interested in a multistage rocket would not be looking at this competition. The easiest way would be to insist that the rocket return in one piece (we already require a single bottle as the pressure vessel).

Yes, I think we should be that clear. Like I said, there are different ways you can interpret the spirit of this competition, and a boosted dart would be in line with one of those interpretations. And as they are right now, I think the rules allow a boosted dart. We could insist the rocket return in one piece, or we could just say the rocket must reach apogee in one piece. I think that's still pretty clear, and it allows people to have the rocket split into multiple pieces, each with it's own parachute. Not sure what the advantage there would be, but I don't see why we should rule it out, either.

Also, as long as the class B record is higher than these, it makes sense to compete in these classes with a boosted dart (if allowed, of course). Personally, I'll probably have a stab at this competition whether or not we allow a boosted dart. So unless anyone else chimes in, we might as well rule it out.

Looks pretty good. For the unreinforced class I can certainly see wanting to keep things simple and not allowing any type of bottle modifications. However, for the reinforced class, I really think we should be a little more open. If the point of this class is to allow people without access to FTCs to compete, I don't see why we should be so restrictive with what we can do with the bottles. Unfortunately, there is no good standard bottle that is available all around the world. As such, I think we should let people be creative to get what ever they can out of the bottles that they have. For example, in some places you can get bottles with nice rounded ends (see D&P Rockets' class C winner- viewtopic.php?f=23&t=700, which appears to have a round bottom and separate stand) while here I cannot. No problem, rounding the end with a heat gun and about 20 psi inside the bottle is about a 30 second job. If was going to take the time to put a carbon sleeve over a bottle with a pentaclaw base, there is no way I would do it without first rounding the bottom. It's such an easy modification that gives such a better shape for the sleeve to conform to. I likely never will put carbon fiber on a single bottle rocket, but I do have another reinforcement technique that I might try to compete in this class with. And that technique also benefits from (requires, for certain bottles) the rounding of the base. Actually, no need to be secretive here- I'm talking about heat shrinking bottles over top of one another. The technique for doing that is exactly the same as the technique for rounding the base of the original bottle- and even if you don't mod the original before adding the second layer, it might happen when you add the second layer. Just depends on how long you hold the heat on it. You are really starting to split hairs if you say "Hey, that inner bottle changed shape a bit when you added your outer layer. It doesn't count."

I really don't mean to be pushy on this issue. I just think that if we are trying to get people competing in the classes, we should allow those modifications that many people already do and that anyone can do. It's too bad we aren't getting more opinions on this. Anyway, if no one has any questions for me, that's the last I'll say on this.

SaskAlex wrote:Looks pretty good. For the unreinforced class I can certainly see wanting to keep things simple and not allowing any type of bottle modifications. However, for the reinforced class, I really think we should be a little more open. If the point of this class is to allow people without access to FTCs to compete, I don't see why we should be so restrictive with what we can do with the bottles. Unfortunately, there is no good standard bottle that is available all around the world. As such, I think we should let people be creative to get what ever they can out of the bottles that they have. For example, in some places you can get bottles with nice rounded ends (see D&P Rockets' class C winner- viewtopic.php?f=23&t=700, which appears to have a round bottom and separate stand) while here I cannot. No problem, rounding the end with a heat gun and about 20 psi inside the bottle is about a 30 second job. If was going to take the time to put a carbon sleeve over a bottle with a pentaclaw base, there is no way I would do it without first rounding the bottom. It's such an easy modification that gives such a better shape for the sleeve to conform to. I likely never will put carbon fiber on a single bottle rocket, but I do have another reinforcement technique that I might try to compete in this class with. And that technique also benefits from (requires, for certain bottles) the rounding of the base. Actually, no need to be secretive here- I'm talking about heat shrinking bottles over top of one another. The technique for doing that is exactly the same as the technique for rounding the base of the original bottle- and even if you don't mod the original before adding the second layer, it might happen when you add the second layer. Just depends on how long you hold the heat on it. You are really starting to split hairs if you say "Hey, that inner bottle changed shape a bit when you added your outer layer. It doesn't count."

I really don't mean to be pushy on this issue. I just think that if we are trying to get people competing in the classes, we should allow those modifications that many people already do and that anyone can do. It's too bad we aren't getting more opinions on this. Anyway, if no one has any questions for me, that's the last I'll say on this.

Alex

Hi Alex,

Thank you for the input.

This is a tough one. How much modification should be allowed before the rocket falls into the class A competition. The biggest challenge is trying to make this competition different enough from the class A and class B competitions. Teams without access to FTC can still compete in class A or B if they splice bottles together to make a long rocket similar to FTC.

Remember that this is not just restricted to soda bottles. Perhaps you could find iced tea bottles, water bottles or even energy drink bottles that would be a more suitable shape. One of the challenges of this competition would be selecting the correct bottle from all of the choices out there.

Nothing is set in stone yet (it says second draft on the top of each page). I appreciate your suggestions and comments.

A big challenge with allowing modifications will be how to police which modifications are allowed or even defining what allowed modifications are and then making sure that there are no grey areas or loopholes which a clever team could exploit. Rounding the bottle bottom would most likely increase the volume of the bottle. What if we specify maximum volume for modified bottles at 2.0 liters (meaning that if you wanted to use your technique of rounding the bottom, you would have to start with a bottle volume of less than 2 liters so that the rounded bottle makes the limit).

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

How much modification should be allowed before the rocket falls into the class A competition. The biggest challenge is trying to make this competition different enough from the class A and class B competitions. Teams without access to FTC can still compete in class A or B if they splice bottles together to make a long rocket similar to FTC.

I guess I'm not sure what I feel the purpose of the reinforced class is. The unreinforced one makes sense to me- very simple rockets that people can build quickly and join in the competition with. However, once you start to reinforce your rocket you are looking at spending more time, and maybe more money on it. Simple "heat gun shape modifying" is a very small effort compared to the actual reinforcement itself. As I said before, I think saying "the only modifications allowed are to alter the shape of the bottle through the use of internal pressure and externally applied heat. The bottle may not be inserted into any type of mold during this process," is fairly clear. This process is far simpler than splicing or reinforcing.

Remember that this is not just restricted to soda bottles. Perhaps you could find iced tea bottles, water bottles or even energy drink bottles that would be a more suitable shape. One of the challenges of this competition would be selecting the correct bottle from all of the choices out there.

One of the biggest reasons I'd like to heat-shape the bottom is to use flat-bottomed water bottles. The correct bottle from all the choices out there might not be available in your area, but heat shaping can make one of your available bottles more like that ideal bottle.

Rounding the bottle bottom would most likely increase the volume of the bottle. What if we specify maximum volume for modified bottles at 2.0 liters (meaning that if you wanted to use your technique of rounding the bottom, you would have to start with a bottle volume of less than 2 liters so that the rounded bottle makes the limit).

Heating causes the plastic to shrink, pressure causes it to expand. It's a balance of the two factors. I think I usually end up with a smaller bottle than I start with. If you end up smaller, it means you used a reasonable pressure and the process was quite safe (flat bottomed bottles will "dome out" and expand even at safe low pressures) .How about final capacity must be less than initial, or no more than 2L (if you start with a smaller bottle)? I'd be alright with final must less than 2L, but I really think you should be able to start with a 2L (which will hold slightly more than 2L) as long as you don't increase it's capacity.

That's a whole lot of input from someone who claims to be trying "not to be pushy". Sorry. If the majority of people just want to keep this competition as simple as possible, that's fine by me.

On a side note- I never really thought that it's the rules of the competitions that keep people away, it's the competition itself. Once the records become "unattainable" to average Joe, he won't be interested in competing. This can happen in any class. I think something that would really get a lot of people involved is a "ladder of challenges". They could be based on altitude, but also functional- a parachute system that will work ten times in a row, capturing onboard video, full class A or class B compliance at a certain altitude, pumping method capable of > 200psi, etc. Obtain all the objectives below a certain level, and you can claim a certain title. It would give people something attainable to work towards, while emphasizing the development process that they would have to go through anyways. Kind of out place, I know. I could move that to a new thread if anyone thinks it worthy of discussion.

"Pressure vessel and fuselage of rocket must be constructed from a single unmodified soft drink bottle which cannot exceed 2 liters (labeled capacity) volume. (commercially produced stretched or modified bottles such as the U14 stretched water rocket bottle by Anti Gravity Research are not allowed).. "

The meaning of "and fuselage" isn't clear to me. I THINK it is being used in a way that excludes payload bay section and nosecone but the way it reads, I feel like I am inferring that. Perhaps it is just my background as an airplane guy that the payload, cabin and fuel tanks are all part of the fuselage.

SaskAlex wrote:How about final capacity must be less than initial, or no more than 2L (if you start with a smaller bottle)? I'd be alright with final must less than 2L, but I really think you should be able to start with a 2L (which will hold slightly more than 2L) as long as you don't increase it's capacity.

This looks good to me. I think modification of the bottle shape should be allowed in the reinforced class.

WRA2 wrote: How much modification should be allowed before the rocket falls into the class A competition.

I don't realy get this, are you assuming that a single bottle can be modified and reinforced that much that it would beat the current class A record?

SaskAlex wrote:How about final capacity must be less than initial, or no more than 2L (if you start with a smaller bottle)? I'd be alright with final must less than 2L, but I really think you should be able to start with a 2L (which will hold slightly more than 2L) as long as you don't increase it's capacity.

This looks good to me. I think modification of the bottle shape should be allowed in the reinforced class.

WRA2 wrote: How much modification should be allowed before the rocket falls into the class A competition.

I don't realy get this, are you assuming that a single bottle can be modified and reinforced that much that it would beat the current class A record?

Hi arjan,

The "reinforced bottle" competition will be a separate competition from the class A with it's own record. The discussion was about deciding how much modification should be allowed in this new competition before the rockets start resembling the class A rockets and thus would make the competition too similar to the class A. We want the difficulty and cost to participate for this competition to fall halfway between the unreinforced bottle and the class A competition.

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

"Pressure vessel and fuselage of rocket must be constructed from a single unmodified soft drink bottle which cannot exceed 2 liters (labeled capacity) volume. (commercially produced stretched or modified bottles such as the U14 stretched water rocket bottle by Anti Gravity Research are not allowed).. "

The meaning of "and fuselage" isn't clear to me. I THINK it is being used in a way that excludes payload bay section and nosecone but the way it reads, I feel like I am inferring that. Perhaps it is just my background as an airplane guy that the payload, cabin and fuel tanks are all part of the fuselage.

~Bugwubber

Hi Bugwubber,

The intention was to exclude the payload section. I'm open to suggestions on a better way to write it. What that really needs to say is :

"Pressure vessel must be constructed from a single unmodified soft drink bottle which cannot exceed 2 liters (labeled capacity) volume. (commercially produced stretched or modified bottles such as the U14 stretched water rocket bottle by Anti Gravity Research are not allowed).. "

Teams can construct the payload as they see fit but must remember that it is included in the total weight of the rocket and that the exterior cannot be metal.

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

How much modification should be allowed before the rocket falls into the class A competition. The biggest challenge is trying to make this competition different enough from the class A and class B competitions. Teams without access to FTC can still compete in class A or B if they splice bottles together to make a long rocket similar to FTC.

I guess I'm not sure what I feel the purpose of the reinforced class is. The unreinforced one makes sense to me- very simple rockets that people can build quickly and join in the competition with. However, once you start to reinforce your rocket you are looking at spending more time, and maybe more money on it. Simple "heat gun shape modifying" is a very small effort compared to the actual reinforcement itself. As I said before, I think saying "the only modifications allowed are to alter the shape of the bottle through the use of internal pressure and externally applied heat. The bottle may not be inserted into any type of mold during this process," is fairly clear. This process is far simpler than splicing or reinforcing.

Remember that this is not just restricted to soda bottles. Perhaps you could find iced tea bottles, water bottles or even energy drink bottles that would be a more suitable shape. One of the challenges of this competition would be selecting the correct bottle from all of the choices out there.

One of the biggest reasons I'd like to heat-shape the bottom is to use flat-bottomed water bottles. The correct bottle from all the choices out there might not be available in your area, but heat shaping can make one of your available bottles more like that ideal bottle.

Rounding the bottle bottom would most likely increase the volume of the bottle. What if we specify maximum volume for modified bottles at 2.0 liters (meaning that if you wanted to use your technique of rounding the bottom, you would have to start with a bottle volume of less than 2 liters so that the rounded bottle makes the limit).

Heating causes the plastic to shrink, pressure causes it to expand. It's a balance of the two factors. I think I usually end up with a smaller bottle than I start with. If you end up smaller, it means you used a reasonable pressure and the process was quite safe (flat bottomed bottles will "dome out" and expand even at safe low pressures) .How about final capacity must be less than initial, or no more than 2L (if you start with a smaller bottle)? I'd be alright with final must less than 2L, but I really think you should be able to start with a 2L (which will hold slightly more than 2L) as long as you don't increase it's capacity.

That's a whole lot of input from someone who claims to be trying "not to be pushy". Sorry. If the majority of people just want to keep this competition as simple as possible, that's fine by me.

On a side note- I never really thought that it's the rules of the competitions that keep people away, it's the competition itself. Once the records become "unattainable" to average Joe, he won't be interested in competing. This can happen in any class. I think something that would really get a lot of people involved is a "ladder of challenges". They could be based on altitude, but also functional- a parachute system that will work ten times in a row, capturing onboard video, full class A or class B compliance at a certain altitude, pumping method capable of > 200psi, etc. Obtain all the objectives below a certain level, and you can claim a certain title. It would give people something attainable to work towards, while emphasizing the development process that they would have to go through anyways. Kind of out place, I know. I could move that to a new thread if anyone thinks it worthy of discussion.

Alex

Hi Alex,

I guess I'm not sure what I feel the purpose of the reinforced class is. The unreinforced one makes sense to me- very simple rockets that people can build quickly and join in the competition with. However, once you start to reinforce your rocket you are looking at spending more time, and maybe more money on it. Simple "heat gun shape modifying" is a very small effort compared to the actual reinforcement itself. As I said before, I think saying "the only modifications allowed are to alter the shape of the bottle through the use of internal pressure and externally applied heat. The bottle may not be inserted into any type of mold during this process," is fairly clear. This process is far simpler than splicing or reinforcing.

The purpose of the reinforced bottle competition is to create an intermediate level competition which the cost and skill level required would fall between the "unreinforced bottle" and the class A or B with the intention that teams would "step" their way up.

Teams would have more choice and could choose their level based on free time, cost, and skill level.
World records would be posted for each class.

Heating causes the plastic to shrink, pressure causes it to expand. It's a balance of the two factors. I think I usually end up with a smaller bottle than I start with. If you end up smaller, it means you used a reasonable pressure and the process was quite safe (flat bottomed bottles will "dome out" and expand even at safe low pressures) .How about final capacity must be less than initial, or no more than 2L (if you start with a smaller bottle)? I'd be alright with final must less than 2L, but I really think you should be able to start with a 2L (which will hold slightly more than 2L) as long as you don't increase it's capacity.

I believe I suggested making a maximum volume requirement but the biggest problem I see is that using heat to "round out" the bottle may lead to a clever team "inflating" their bottle to significantly increase the volume (It would not matter how thin the walls got if they reinforced it using other material such as wrapping in fiberglass cloth and resin).

On a side note- I never really thought that it's the rules of the competitions that keep people away, it's the competition itself. Once the records become "unattainable" to average Joe, he won't be interested in competing. This can happen in any class.

World records are supposed to be hard to attain. The rules must remain though as eventually someone comes along and wants to challenge a record. The rules ensure that the effort by the challenging team can be compared equally to the sitting record holder. Even if no one participates in a particular competition for years, eventually someone will want to.

On a side note- I never really thought that it's the rules of the competitions that keep people away, it's the competition itself. Once the records become "unattainable" to average Joe, he won't be interested in competing. This can happen in any class. I think something that would really get a lot of people involved is a "ladder of challenges". They could be based on altitude, but also functional- a parachute system that will work ten times in a row, capturing onboard video, full class A or class B compliance at a certain altitude, pumping method capable of > 200psi, etc. Obtain all the objectives below a certain level, and you can claim a certain title. It would give people something attainable to work towards, while emphasizing the development process that they would have to go through anyways. Kind of out place, I know. I could move that to a new thread if anyone thinks it worthy of discussion.

Sounds like a good idea to discuss once we are finished with this competition. A couple of things I had in mind was to create a set of rules for "educational" competitions (most likely some kind of distance competition where rockets would not need any recovery systems or electronics. That way Schools could compete and compare using a universal set of rules. We will look for ideas for that and your suggestion as soon as the rules are adopted for the new bottle classes.

A thought for a reward for completing your objectives might be to give "merit badges" or ranks to the team's form account (our record holders right now have extra avatars that display when posting to identify what record that they are holding). That would give teams the incentive to participate.

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

I believe that everyone pretty much agreed on the competition rules for the unreinforced bottle and we will soon be able to put them up for a ratification vote. For the reinforced class, there was still some discussion about what kind of modifications teams could make to the bottle. Here is a suggestion for the discussion. What about allowing bottles that weren't soft drink bottles into the reinforced competition (unmodified). Since the bottle would be reinforced, other types of bottles could be used (shampoo bottles, water bottles, iced tea bottles, ketchup bottles and the list goes on and on). That way teams would have a much bigger choice in bottle shape.

Comments?

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association

WRA2 wrote:What about allowing bottles that weren't soft drink bottles into the reinforced competition (unmodified). Since the bottle would be reinforced, other types of bottles could be used (shampoo bottles, water bottles, iced tea bottles, ketchup bottles and the list goes on and on). That way teams would have a much bigger choice in bottle shape.

I must say, I've been misreading the current rules. I thought we already were saying "beverage bottle", and didn't realize "soft drink" was still specified. I certainly think things like iced tea and water bottles should be allowed- most of them are made from the same stretch-blow-moulded PET as pop bottles, but sometimes in different formats. I don't see how ketchup bottles would be useful, and I don't see how we would word it to allow those kinds of things without making it too open. My suggestion would be "non-alcoholic plastic beverage bottle". I'm not too concerned about the non-alcoholic part, but some of those bottles are a lot thicker, and allowing them would put under-aged competitors at a slight disadvantage.